My answers to some of your questions...you may get varied opinions and you should fairly consider everyone's opinion.
2.Lets say I successfully transfer the coins to my ledger, I am concerned the same thing (losing BTC) will happen if I transfer my BTC to an exchange. Again, how likely are such scenarios
It's as likely as it would be likely for you to mis-type the destination Bitcoin address into your Ledger "send bitcoin" screen prompts.
3.In the event where bitcoin does reach 100K, and we intend to sell on an exchange, who can realistically buy these at such exorbitant prices. No use having 1 million BTC if you can't sell it
The lowest potential transactional increment of a bitcoin is 1 satoshi,
BTC0.00000001, which is 1 / one hundred millionth of a bitcoin. Today you probably couldn't get a one satoshi transaction confirmed, but in theory it is feasible. The fact that bitcoin transactions can be denominated down to 8 places after the decimal means you can easily transact in a fiat volume that makes sense at the time of your transaction. With Bitcoin at $100,000, if you wanted to transact $1,000 it would be
BTC0.01. A normal transaction size!
4.I've read that transaction fees are going through the roof, could it scale to a level where transferring 1million BTC would result in fees amounting to 500K for example?
I guess anything's possible and I can't offer an educated opinion on how high fees are projected to get. But if fees get to unfair levels you could trade your Bitcoin for an alternative crypto-currency that offers lower fees...Litecoin would be a good option, they have lower fees now and could have lower fees than Bitcoin in the future.
Good luck with your first major purchase! Hodl forever!